Regional differences and round-by-round dynamics of aldehydes in sauce-flavor baijiu from the Chishui River Basin

Sauce-flavor baijiu derives its characteristic aroma from the unique geography of the Chishui River Basin and a multi-round fermentation process. Aldehydes are key odorants contributing fruity, roasted, and nutty notes, yet their regional distribution and evolution across the seven production rounds remain poorly characterized. We developed a GC-FID method to quantify aldehydes in eight commercial baijiu samples from seven production regions and monitored acetaldehyde, acetal, and furfural across the seven rounds of baijiu. The method showed excellent linearity (R 2  ≥ 0.996), low detection limits (0.02–0.30 mg/L) and high precision (RSD ≤ 3.12%). Regional aldehyde profiles differed significantly ( P  < 0.05). Multivariate analysis clearly separated samples by origin and identified the three compounds as high-VIP concentration variables (VIP > 1). Across rounds, acetaldehyde and acetal exhibited a rise-fall-rise pattern, while furfural increased steadily. Acetaldehyde was more sensitive to region and processing conditions, furfural showed cross-regional consistency, and acetal was intermediate. These findings provide a chemical basis for origin authentication, round-based grading and process optimization in sauce-flavor baijiu production.